In water treatment such as water purification treatment and drainage water treatment, various methods have been examined for solid-liquid separation of treatment target water by using a membrane module having a separation membrane such as a microfiltration membrane or an ultrafiltration membrane. When the treatment target water is filtered by using the separation membrane, treated water with high water quality can be obtained. As a method for solid-liquid separation of the treatment target water, specifically, there is known a method of performing solid-liquid separation by a large number of hollow fiber membrane modules each obtained by resin-fixing a sheet-like hollow fiber membrane to a housing. Further, there is also known a method of collecting and extracting filtrate by water-tightly connecting a large number of membrane elements to a cylindrical water collection header provided with holes for connecting membrane elements.
Patent Literature 1 discloses a water collection header configured as a hollow pipe provided with a plurality of connection ports to which a water collection pipe of a membrane module is connected. In the water collection header, a plurality of holes are opened in one hollow pipe and a sleeve pipe is attached to each hole to form the connection port. For that reason, a plurality of connection ports each having a sleeve pipe provided in an elongated hollow pipe are formed in response to the number of the membrane modules.
Patent Literature 2 discloses a water collection header including a water collection member and a membrane module connection member provided with a hole for connection to a membrane module. In the water collection header, a dimension change absorption portion is provided between the membrane module connection member and the water collection member. In the water collection header, the elongated membrane module connection member is provided with a plurality of holes corresponding to the number of the membrane modules.